This invention relates to a system for augmenting the visual and radar characteristics of an airborne target and more particularly to such a system which embodies a light source mounted behind a radar reflector with the reflector itself being so constructed and arranged that it is essentially transparent to light and reflective insofar as radar wavelengths are concerned.
Heretofore in the art to which my invention relates, many systems have been proposed for augmenting the visual and radar characteristics of small airborne targets, such as towed targets. However, with such systems, it has been impossible to employ conventional components due to the blocking effect the reflector, commonly constructed of a non-transparent material, presents to the light source or vice-versa. Heretofore, this problem could only be overcome by mounting either the light source or the reflector external to the target to achieve both radar and visual coverage in a common sector. This type mounting arrangement is unsatisfactory where small targets having low aerodynamic drag are required. One system heretofore tried has consisted of an aircraft landing light mounted behind a clear plastic nose cone with the radar augmentation consisting of a traveling wave tube amplifier with receiving and transmitting antennas. The heavy weight of this system was determined to be excessive for the limited capability of the tow system used. Additionally, the target was too expensive for its intended use.
Another approach to solving the problem of providing both radar and visual augmentation in the forward aspect sector of the target was to use a constant-K lens radar reflector constructed of a clear material mounted in the nose of the target with a light source mounted at the focal point on the lens. However, focusing, heat dissipation, and light attenuation problems proved to be insurmountable from the standpoint of practical cost considerations.
A further approach to the problem was to mount a standard Luneberg lens, opaque to light, in the nose of the target and employ a light source which works through an optics link in the body of the target. The light was to be focused on a small rotating mirror housed inside a plastic bubble located on the underside of the target. However, due to the fact that the light source in such an arrangement was critical from the standpoint of point source properties and the bubble on the bottom of the target presented excessive drag, the cost of materials combined with the manhour cost for alignment of the optic system made the system too expensive. It will thus be seen that many systems heretofore proposed have been abandoned for reasons of cost and aerodynamic drag.